Simultaneous extrusion of insulation and connecting webs joining pairs of insulated conductors to form an insulated joined conductor pair, easily traced through a cable, have now become relatively common in communication cable manufacturing, as exemplified by my patents U.S. Pat. Nos. 3,361,871 and 3,383,736. Over the past century, a number of proposals have been disclosed in issued United States Patents for extrusion of multi-conductor cables: U.S. Pat. Nos. 9,989; 1,500,546; 2,628,998; 2,979,431; 3,728,424; and 3,757,029 are all examples of such patents.
The extrusion die assembly apparatus illustrated and described in these patents has not proved effective in the extrusion of miniature ribbon cables incorporating extremely fine conductor wires. Accordingly, a significant need has developed for methods and apparatus capable of producing extruded ribbon cable in fine miniature sizes.
Wire breakage has proved to be a difficult problem, since one broken wire destroys the effectiveness of the entire ribbon cable, and until it is discovered and a new unbroken wire is introduced, a long span of defective cable can be produced by conventional extruding apparatus. Even after the broken conductor is discovered, the threading insertion of a new fine conductor wire through the die is a nearly insurmountable problem.
Furthermore, in ribbon cables incorporating extremely fine conductor wires, a comparably thin layer of insulation is desired to reduce the size and weight of the final extruded cable. With conventional extrusion dies, however, the desired minimum insulation thickness requires highly critical positioning of the conductor wires within the extrusion die, since a slight displacement of the conductor wires toward one surface of the extruded ribbon cable can reduce or totally eliminate the thin insulation layer from that side of the cable. Interconductor capacitance producing "cross-talk" in communication cables is best minimized by uniform spacing and uniform insulation of the ribbon cable conductors, and high quality miniature ribbon cable has not been available in the past because these manufacturing problems have remained unsolved.